The Draft IEEE 802.16m system Description document, IEEE 802.16m-08/003r1, dated Apr. 15, 2008, provides that the IEEE 802.16m amendment to the IEEE 802.16 standard is intended to “provide performance improvements necessary to support future advanced series and applications . . . . ” As additional background to the present application, the IEEE 802.16 standard is incorporated herein by reference.
Known wireless communications schemes may involve the use of a single antenna or multiple antennas on a transmitter and/or receiver. A multiple-input, multiple-output (MIMO) wireless communication system has multiple communication channels that are used between a plurality of antennas at a transmitter and a receiver. Accordingly, in a MIMO system a transmitting device will have N antennas, and a receiving device will have M antennas. Space-time coding controls what data is transmitted from each of the N antennas. A space-time encoding function at the transmitter processes data to be transmitted and creates unique information to transmit from the N antennas. Each of the M antennas will receive signals transmitted from each of the N antennas. A space-time decoding function at the receiving device will process the information sent from the N antennas to recover the data.
It has been recognized that as compared to with older, conventional technology, a MIMO wireless communication system provides an improvement in range and capacity of a connection between a client (e.g. a mobile communications device) and an access point (e.g. a base station). This in turn, is understood to typically result in, among other things, more reliable signal quality, a larger bandwidth connection and increased overall system throughput.
In practice, integrating multiple receive antennas at a client, especially small client devices such as mobile communications devices, has been a challenge for a number of reasons, including, but not limited to, reduction in the size of each antenna to fit in a space-constrained environment and obtaining sufficient operational bandwidth from the small antennas. Other problems include undesirable interaction between antennas that are physically located near each other. For these reasons, and others, mobile communications devices typically only supported a single antenna.
Consequently, while communications between certain components of wireless communication systems may have employed MIMO modes/techniques (e.g. between base stations and relays, where the base station and relay may have multiple transmit antennas), little emphasis was placed on developing or employing MIMO modes in uplink transmissions (i.e. transmissions from a mobile communications device to a base station) due to the relative unavailability of multiple (i.e. more than one) transmit antennas at mobile communications devices.
However, with recent technological advances, mobile communications devices with multiple antennas have become available. Therefore, the use of MIMO techniques/modes in uplink communications has become desirable, as it is expected to result in, among other things, increased data transmission rates from mobile communications devices. This is turn is expected to provide improved user experience.